Recently, with the active development of electric vehicles, storage batteries, robots, satellites, and the like, along with the dramatically increasing demand for portable electronic products such as laptop computers, video cameras, mobile phones, and the like, research and development for high-performance secondary batteries capable of repeatedly charging and discharging has been actively made.
Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a cathode active material and anode active material, respectively. The lithium secondary battery includes an electrode assembly in which a cathode plate and an anode plate respectively coated with the cathode active material and the anode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
In these days, secondary batteries are widely used not only for small-sized devices such as portable electronic devices but also for middle-sized or large-sized devices such as vehicles and power storages. In particular, along with exhaustion of carbon energy and increased interest on environments, the public attention is focused on hybrid vehicles and electric vehicles over the world, including USA, Europe, Japan and Korea. In such hybrid vehicles and electric vehicles, the most essential part is a battery pack which gives a driving force to a vehicle motor. A hybrid vehicle or an electric vehicle ensures better fuel efficiency and exhausts no or less pollutant substances since a driving force for a vehicle is obtained by charging/discharging a battery pack. For this reason, more and more vehicle users select such hybrid vehicles and electric vehicles. In addition, the battery pack of the hybrid or electric vehicle includes a plurality of secondary batteries, which are connected in series or in parallel to enhance capacity and output.
Meanwhile, the battery pack may include various electric parts together with a plurality of secondary batteries, and these electric parts are called electrical equipment. The electrical equipment included in the battery pack representatively may be a relay, a current sensor, a fuse, a battery management system (BMS) or the like. Such electrical equipment serves as a component for managing charging/discharging of a secondary battery included in the battery pack and ensuring safety, and is essentially included in most kinds of battery packs.
In case of an existing battery pack, such electrical equipment is mounted to an inside or outside of the battery pack, but this electrical equipment arrangement causes several problems. For example, in an existing battery pack, in order to ensure a space for mounting a plurality of electrical equipment, it is required to increase a volume of the battery pack or decrease an accommodation space of the secondary battery. In addition, in an existing battery pack, it is not easy to dispose and assemble each of electrical equipment to an inside or outside of the battery pack, and it is also not easy to connect the electrical equipment to a battery module included in the secondary battery. Moreover, in an existing battery pack, if any part of the electrical equipment needs to be exchanged due to a breakdown, it is not easy to exchange the part since the electrical equipment is installed with a complicated structure.